Temperature regulating means for



Patented June 20, 1939 UNITED STATES PATENT OFFICE TEMPERATURE REGULATING MEANS FOR METALLURGICAL FURNACES Application June 18, 1936, Serial No. 85,976

4 Claims.

This invention relates to temperature regulating means for metallurgical furnaces and more particularly to means for automatically regulating the temperatures of furnaces, such'as a soak- 5 ing pit furnace, which are employed in metallurgical processes for the purpose of heating ingots and batches of metal to a uniform temperature in preparation for mechanical deformation. Such furnaces are customarily fired and dampered alternately. The present practice in connection with such furnaces is to regulate the .firing and dampering manually. This results in a waste of fuel and an irregularity of temperatures, and frequently an unnecessary and unde-.

l sirable degree of oxidation of the heating metal. 'It is usual to heat such furnaces-with a mixture of fuel andair under .pressure.

One of the objects of the present invention is to provide means to automatically regulate 20 and control the temperatures of furnaces which are alternately fired and dampered.

Another object is to provide means to automatically turn off and on the fuel and air supply to the furnace and to open and close the 25 damp-er means of the said furnace in a determined sequence and at determined time intervals, which means is operated by and in response to the thermal conditions obtaining in the furnace.

30 Still another object is to provide an automatically operative means for-insuring an economical operation of the furnace and efficient maintenance of furnace temperatures during operating use of the furnace.

35 Other objects and advantages will be'apparent as the invention is more fully disclosed.

Before further disclosure of the present invention reference should be made to the accompanying drawing wherein the temperature reg- 40 ulating and control means of the present invention is schematically,illustrated in association with a typical furnace adapted to be alternately fired and dampered.

Referring to the drawing, furnace l is a 45 typical soaking pit furnace. A hearth 2 is provided in furnace I upon which metal articles to be heated are disposed and the furnace I communicates through flue 3 to stack 4 to permit the escape of heated gases therefrom.

0 Burner means 5 is provided for heating furnace I and damper means 6 is provided for closing flue 3 to prevent the escape of heated gases from furnace I to stack 4 when desired. Burner 5 is adapted to burn a mixture of fuel and air sup- 55 plied thereto through valves 1 and 8 respectively. Cover 9 closes furnace I from the atmosphere and is adapted to be moved horizontally along track II] by means II operating through means I2 into and out of furnace closing position as is customary in the art. 5

In such a furnace it is customary to supply heat energy through operation of burner 5 to furnace I until the desired furnace temperature is attained therein, and then by alternate operation of burner 5 and damper 6 to maintain 10 this temperature as closely as possible over the time interval desired. It frequently happens however, that while the operator may shut off the fuel supply to burner 5 the air supply is left on thereby oxidizing the heated metal on hearth 2; or the damper 6 is not closed thereby losing a lot of heat. On opening cover 9 the operator may shut off the fuel to burner 5 and fail to shut off air or fail to open or close damper 6. Therefore, in accordance with the objects of the present invention we provide means to accomplish all of these operations automatically and in proper sequence to the end that a precise control over thermal and atmospheric conditions in the furnace may be obtained.

To accomplish this result we dispose a thermal sensitive device, such as pyrometer I3, in one wall of the furnace I in such position as to be responsive to thermal conditions therein..- The pyrometer I3 is electrically connected-to pyrometric controller I4 which actuates a movable contact C. Two sets of control contacts A and B are disposed in such position with respect to contact C as to be contacted therewith when the said contact C is moved up scale and down scale respectively. Contacts A and B are adjustable along the scale to thereby provide upper and lower temperature limit switches respectively. This recorder device and associated contacts are common in the ,art and needs no further description as to its particular mode of operation.

Upon actuation of contact C in either direction the closing of contacts A or B energizes an electrical circuit which actuates means adapted to perform in sequence and at proper time intervals the shutting off or turning on of fuel valve I; or air valve 8; or the closing or. opening of damper 6.

When contact C engages contacts B, which is the maximum temperature limit, for example, the electrical circuit closed thereby energizes a reversing electrical motor (M) in one direction which operates a gear reduction unit (G) which drives shaft (S). Upon shaft S are mountfurnace and means operatively connecting the a said first mentioned means with said cover to energize the said first means upon opening andclosing the said cover, the opening of the cover operating to energize said first means identically as though the upper temperature limit had been attained by said recorder device and the closing of the cover operating to place said first means in position to operate with the attaining of the lower temperature limit by said recorder device.

' 2. In combination a furnace, a fuel burner for heating said furnace, a stack communicating with said furnace, damper means to shut off and to open the said stack to the flow of gases from said furnace, a thermal sensitive device disposed in a position tobe energized by the heat energy within said furnace, a recorder device, a movable contact arm on said recorder device, and adjustable contacts on opposite sides of said arm to limit the movement of said arm in two directions, an electrical circuit including said thermal sensitive device and said recorder device adapted to actuate the said arm responsive to the energization of said thermal device by heat energy from said furnace, a second electrical circuit including said adjustable contacts and including means actuated by the contacting of said arm with one of the contacts to shut on the fuel to said burner to shut off the air supply to said burner and to close the said damper in the recited sequence and at timed intervals, means actuated by the contacting of said arm with the other of said contacts to open said-damper, to turn on said air supply and said fuel supply in the recited sequence and at timed intervals, a removable cover for said furnace, and means actuated upon the removal of said cover to energize the first mentioned means of said'second electrical circuit irrespective of the position of said movable contact arm and upon the closing of said cover to restore the said circuits to an operative position responsive to a contacting of said arm with the said other contact.

3. In combination with a furnace of the soaking pit type provided with a stack, damper means to regulate the passage of heated gases from the furnace to the stack, and burner means to supply burning gases to the interior of said furnace,

means to regulate and control the temperatures attained in said furnace, the supply of fuel and air to the said burner and the operation of said damper, said means including a pyrometer disposed in a position to thermally indicate the furnace temperatures, a recorder device opera,- tively connected therewith to record the indicated temperatures, adjustable temperature limit switches on said recorder device adapted to set maximum and minimum temperature limits, an electrical circuit connected to said switches adapted upon the closing of either one of the said switches to energize mechanism adapted to turn on or off the fuel and air supply to the furnace and to open or close the said damper means in'a determined sequence and at determined intervals, said sequence being upon closing of upper limit switch to turn off fuel, then air and then close damper and upon closing of lower limit switch to reverse this operation, a cover for said furnace and means operative upon the opening of said cover to energize the said mechanism to operate identically the same as when said upper limit switch is closed and upon closing said cover to restore said circuit to position adapting the same to energize said mechanism upon the recorder device recording a temperature adapted to close the lower temperature limit switch.

4. In combination, means for controlling and regulating the temperatures of furnaces of the soaking pit type, said means comprising a pyrometer disposed in a position to indicate the thermal condition in said furnace, a recorder device adapted to record the indicated temperatures, adjustable upper and lower temperature limit contacts on said recorder device and a switch arm operatively engaged with the recording element of said recorder device in a position to engage said contacts upon being moved to upper and lower limit temperatures respectively, a reversible motor and an electrical circuit for energizing said motor in opposite directions upon the closing of the said upper and lower contacts respectively, and means actuated by the energization of said motor in one direction incident to the closing of the upper limit contact to shut off the fuel and air supply to the furnace and to close the damper means of said furnace in such sequence and at timed intervals, and adapted to reverse said sequence upon the closing of the lower limit contact with consequent energization of the motor in the opposite direction, means actuated by the opening of the door of said furnace to energize said motor in'the same direction obtained through the closing of said upper limit switch and to electrically disconnect said recorder device from said' electrical circuit, and actuated upon the closing of said door to return said recorder device in said circuit and to automatically disconnect said means.

ROBERT H. CANTRELL. LEWIS RUMFORD, II.

C. CARDILLO June 20, 1939.

BRACKET Filed May 5, 1958 

